Optical telecommunications networks use light transmitted along an optical path between a transmitter and a receiver to transmit light signals at high rates of speed over generally long distances. Typically, the optical path is comprised of optical fiber with a multitude of different types of optical devices disposed along the optical path to perform different functions in the network. The optical fiber generally consists of a core, which guides the light signal, and a surrounding cladding, which retains the light signal in the core through total internal reflection. The optical devices must be connected to and optically aligned with ends of the optical fiber in order to properly transmit the light signals. Increasingly, the optical devices are in the form of planar optical waveguides.
Planar optical waveguides can be formed by using various materials, such as polymers, glasses, semiconductors, and composite materials as the core and surrounding cladding material, with the core material having a refractive index slightly higher than that of the cladding material in the near infrared region of the optical telecommunication wavelength window. Various optical devices, such as integrated splitters, couplers, arrayed waveguide gratings, and optical waveguide amplifiers can be formed with planar optical waveguides. In order to insert optical waveguide devices into optical fiber communication networks, it is essential to have the capability to connect optical fibers to waveguides.
Currently available technology for connecting optical fibers to planar optical waveguides uses adhesive bonding, such as epoxy, combined with precision alignment before and during the bonding process. With long exposure to signal light and environmental effects, the adhesive in the optical path between the fiber and the waveguide can suffer, resulting in increased optical absorption and scattering induced performance degradation.
In a typical prior art method of fiber attachment to a planar optical waveguide, a pre-made fiber attachment subassembly constructed of fiber optic capillary tubes or silicon V-groove arrays is polished at an endface that will be attached to an optical waveguide. The optical waveguide is diced and polished at its endface prior to attachment with the fiber attachment subassembly. The fiber attachment subassembly and the optical waveguide chip are positioned on a six-degrees-of-freedom precision alignment station. After fine mechanical adjustment of the fiber attachment subassembly with the waveguide that produces maximum translational and rotational alignment between the core of the optical fiber and the core of the optical waveguide, an adhesive, such as epoxy, is dispensed between the optical fiber attachment subassembly and the waveguide. The adhesive subsequently undergoes curing, such as by ultra-violet light exposure or thermal treatment, which fixes the relative positioning between the fiber on the fiber attachment subassembly and the waveguide. Due to the fact that single mode optical fiber cores and single mode optical waveguide cores have dimensions in the order of micrometers, the alignment tolerance to achieve acceptable level of optical loss between thr fiber and the waveguide is on the sub-micron level. Further, as the adhesive between the fiber and the waveguide is being cured, in-situ readjustment of the alignment between the optical fiber and the optical waveguide is often required because of adhesive volume shrinkage-induced alignment change.
It would be beneficial to provide a process for attaching an optical fiber attachment subassembly with a planar optical waveguide without the need for an adhesive and without the need for in-situ adjustment of alignment during the attachment process.
Briefly, the present invention provides an optical waveguide assembly comprising an optical waveguide having a substrate having a substrate face, a cladding disposed on the substrate, and a waveguide core disposed within the cladding. The waveguide core has a waveguide core face such that the waveguide core face is aligned with the substrate face. The assembly further comprises a fiber support assembly having a support face in contact with the substrate face and a fiber having a fiber core optically aligned with the waveguide core face. Non-adhesive means fixedly connects the substrate face to the support face.
Further, the present invention provides a method of connecting an optical waveguide to an optical fiber support. The method comprises providing an optical waveguide having a substrate, wherein the substrate has a substrate face; providing an optical fiber support having a support face; applying non-adhesive means to at least one of the support face and the substrate face; and contacting the support face and the substrate face.
The present invention further provides a method of connecting an optical waveguide to an optical fiber support. The method comprises providing an optical waveguide having a substrate, wherein the substrate has a substrate face; providing an optical fiber support having a support face; providing a bonding plate having a first portion and a second portion; applying non-adhesive means to at least one of the first portion and the substrate; applying the non-adhesive means to at least one of the second portion and the support; and contacting the first portion to the substrate and contacting the second portion to the support such that the substrate face and the support face are contacting each other.